This relates generally to testing wireless electronic devices, and more particularly, to calibrating test equipment that is used to test wireless electronic devices.
Wireless electronic devices typically include transceiver circuitry, antenna circuitry, and other radio-frequency circuitry that provides wireless communications capabilities. During testing, wireless electronic devices under test (DUTs) can each exhibit different performance levels. For example, each wireless DUT can exhibit its own output power level, gain, frequency response, efficiency, linearity, dynamic range, etc.
The performance of a wireless DUT can be measured using a test instrument. A wireless DUT is typically connected to a test instrument using a radio-frequency cable. There is a path loss associated with a given radio-frequency cable. This path loss is defined as the power attenuation of an electromagnetic signal as it propagates through the radio-frequency cable.
Multiple test stations may be used to test multiple wireless DUTs in parallel, where each test station includes its own test instrument, radio-frequency cable, and test fixture connected in series. A DUT is connected to the test fixture of each test station during test operations. The radio-frequency path of each test station has its own unique path loss characteristic.
In an effort to take into account the radio-frequency cable path loss, a vector network analyzer (VNA) can be connected to each cable to determine its path loss. However, calibrating path loss using this approach requires a VNA and ignores path loss associated with the test fixtures and potential variations that may exist among the different test instruments in the different test stations. Failing to account for test fixture path loss and variations in the behavior of the different test instruments may result in inconsistent measurement data. For example, performance parameters measured using one test station may be offset with respect to the performance parameters measured using another test station.
It would therefore be desirable to be able to provide improved calibration techniques for calibrating wireless test equipment.